Pharmacology of natural compounds. I. Smooth muscle relaxant activity induced by a Ginkgo biloba L. extract on guinea-pig trachea.

A standardized Ginkgo biloba L. extract containing flavonol glycosides induces a concentration-dependent relaxation of guinea-pig trachea in vitro and antagonizes in vivo bronchoconstriction induced by various agonists. The action of the extract appears to be mediated partially by an interaction with the eicosanoid system particularly through specific stimulation of the PGE2 biosynthesis and partially by beta-adrenoceptor activation. The relaxation of guinea-pig trachea induced by the extract is in fact antagonized by indomethacin (2 x 10(-8)M), ETYA (3.4 x 10(-8)M) and sotalol (4 x 10(-6)M). The concentration-response curves obtained with tracheal preparation from reserpinized guinea-pig and those performed in the presence of a glutathione depletor (CDNB 1 x 10(-5)M) are modified in a similar manner confirming that the extract can act on both the systems: adrenergic as well as prostaglandinergic.